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M8- Oral streptococci Flashcards

1
Q

what flora does the mouth have?

A

complex microbial flora

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2
Q

how does oral flora vary?

A

vary from site to site and in disease

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3
Q

Give some examples of gram +ve cocci.

A 
• Aerobic - Micrococcus 
• Anaerobic - Peptococcus
- Peptostreptococcus
•  Facultative
Catalase +ve Staphylococcus
Catalase –ve Streptococcus
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4
Q

what bacteria is found most in the mouth and can be cultivated from all oral sites?

A

oral streptococci

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5
Q

how does streptococci comprise?

A
  • 23% bacteria of approximal dental plaque
  • 30% bacteria of gingival crevice
  • 50% bacteria of the tongue
  • 50% bacteria of saliva
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6
Q

how does strep as facultative anaerobe effectively damage the tooth?

A

by product is lactic acid which causes damage to tooth surface

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7
Q

what type of anaerobes can strep species be?

A

Facultative & Obligate anaerobes

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8
Q

what are the 4 main groups of strep species?

A
  • mutans
  • salivarius
  • anginosus
  • oralis
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9
Q

which 3 groups are alpha haemolytic?

A
  • mutans
  • salivarius
  • oralis (Mitis)
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10
Q

what group is beta haemolytic?

A

anginosus

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11
Q

where is S. mutans found?

A

tooth surface (fissures)

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12
Q

where is S. salivarius found?

A

tongue

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13
Q

where is S. anginosus found?

A

dental plaque and abscesses

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14
Q

where is S. oxalis found?

A

tooth (biofilm/plaque)

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15
Q

what percentage of each strep species makes up 23% of bacteria of approximate dental plaque?

A

– mutans streptococci -2%
– S. sanguinis -6%
– S. salivarius- 1%
– S. anginosus gp. -0.5%

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16
Q

what haemolysis is oral or viridian’s streptococci ?

A

alpha

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17
Q

what haemolysis is pathogenic streptococci ?

A

beta

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18
Q

how does alpha look on a blood agar plate?

A
  • Partial haemolysis - green

- most oral strep

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19
Q

how does beta look on a blood agar plate?

A
  • complete hemolysis - clear haemolysis

- S pyrogens

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20
Q

how does gamma look on a blood agar plate?

A
  • No hemolysis

- eneterococcus faecalis

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21
Q

what is dental caries?

A

Localised dissolution of the enamel

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22
Q

where can caries advance to?

A

dentine and pulp

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23
Q

where is dental caries common?

A

pits and fissures (stagnation sites)

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24
Q

What causes demineralisation of enamel?

A

Bacteria under anaerobic conditions are using carbohydrate and producing lactic acid which dissolves enamel

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25
what Step group is the leading cause of tooth decay?
mutans group
26
what species are in the mutans group?
- streptococcus mutans | - S. sobrinus
27
what does mutans bind to?
bind to and colonise the tooth surface - produce extracellular polysaccharides (sucrose)
28
what is acidogenic?
produces acid at a high rate from sugar
29
what is aciduric?
tolerate high concentrations of acid
30
Name some carbohydrates.
* Glucose * Fructose * Sucrose * Lactose * Galactose * Mannose * Celliobiose
31
Explain Koch's postulates.
* The microorganism is present in every case of the disease but absent from healthy organisms * The suspected organism must be isolated and grown in a pure culture * The same disease must result when the isolated microorganism is inoculated into a healthy host * The same microorganism must be isolated again from the diseased host. * The Ab to the organism should be detected in the patient’s serum
32
what can be used to identify patients susceptible to dental caries?
mutans streptococci count kits
33
what is the heterogeneous group of related strep?
Oralis (or Mitis group)
34
Name 3 species in the oralis group.
- S. oralis - S. sanguines - S. gordonii
35
what do most of the oxalis group produce?
IgA protease (important virulence factor)
36
what does S. sanguinis and S. gordonii produce?
produce extra-cellular soluble & insoluble glucans
37
when does the oxalis group colonise on the pellicle?
Early
38
What disease can strep. sanguinis result in?
bacterial endocarditis
39
how does Strep sanguinis bind to the tooth surface?
by lectin-carbohydrate & non-lectin
40
what does Strep sanguinis bind?
salivary amylase and IgA
41
what does Strep sanguinis act as?
tether for other bacteria
42
what can Strep sangunins interfere with?
may interfere with colonization by S. mutans
43
How can S. sanguinis cause endocarditis?
• S. sanguinis enters the blood after oral trauma – e.g. tooth extractions, subgingival scaling, toothbrushing and chewing, bacteraemia • Bacteria settle on damaged endocardial surfaces causing a bacterial vegetation – i.e. - infective endocarditis
44
what was historically used to treat endocarditis?
Historically antibiotics used for at risk patients – Prophylaxis antibiotics 1 hour before dental treatment • No longer recommended by NICE!
45
what is strep gordonii closely related to?
S. sanguinis
46
what does strep gordonii produce?
alpha amylase | instead of S. sanguinis which produces IgA protease
47
what does alpha amylase binding do?
marks bacterial surface antigens and allows the organism to evade the host defences
48
what can Strep gordonii bind to on the tooth surface?
polysaccharides and starch already deposited on the tooth surface
49
what does strep gordonii cause?
infective endocarditis
50
what does PadA surface protein do?
- adhesion | - interacts with platelets via fibrinogen receptor
51
where is strep mitis found?
Although found in dental plaque, preference of non-keratinized surfaces in the mouth – cheek,ventral surface of the tongue
52
what can strep mitis cause?
bacteraemia, endocarditis and abscesses
53
Describe strep crista.
• Similar to S. sanguinis but with tufts of fibrils on surface • Classically component of “corn-cobs” - bacterial complexes often seen in dental plaque
54
what are the isolation frequencies of streptococci from infective endocarditis?
``` S. sanguinis -32% S. oralis- 30% S. gordonii -13% Others: - no other species exceeds 5% ```
55
Name the dominant species in oral cavity throughout life isolation ; mouth, upper respiratory tract and GI tract.
S. salivarius
56
what surfaces does salivarius group prefer?
Keratinised surfaces: – Commonly found on dorsum of the tongue and in saliva – One of the first bacteria to colonise in the mouth - within hours of birth
57
where is S salvarius not normally found?
plaque – does not stick to teeth – Pili, fibrils, saliva binding proteins & host cell binding proteins – produces fructose polymers (levans) and not glucans as the polysaccharide
58
How can S salvarius be beneficial microbes?
Some strains produce Bacteriocins – Small antimicrobial peptides – Salivaricin A & Salivaricin B
59
what infections can salvarius be associated with?
Pharyngitis, tonsillitis, otitis media
60
Describe S. vestibularis.
• Non-pathogenic, non-polysaccharide producing – inhabitant of the oral vestibular mucosa
61
Name species in the anginosus group.
S. anginosus S. constellatus S. intermedius (opportunistic pathogens)
62
where are the anginosus group found?
dental plaque
63
what infections are anginosus group species isolated from?
– oral abscesses & brain, liver – bacteraemia and endocarditis – appendicitis and peritontitis
64
what are the different habitats of oral streptococci species?
S. sanguinis, S. mutans - tooth surfaces S. salivarius - salvia and tongue S. mitis -oral epithelia
65
Describe S pneumoniae .
– α-haemolytic – N.B. sensitive to optochin – carriage as high as 70% – spread by coughing/sneezing
66
what is sensitive to bacitracin?
S. pyroxenes (beta)
67
what is resistant to bacitracin?
- S. pneumoniae (alpha) - Viridans (alpha) - E. facials (gamma)
68
what is sensitive to optochin?
S. pneumoniae
69
what is resistant to optochin?
- S. pyogenes - Virdians - E. facealis

Microbiology (30 decks)

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